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“An integral transform with scale invariance like the Fourier transform has shift invariance.” From my perspective, it’s useful for analysing multiplicative products of random variables, their reciprocals and powers, much as the Fourier transform is useful for sums of scaled random variables.
For now, see the Mellin transform on Wikipedia.
Approachable references seem to be Bertrand, Bertrand, and Ovarlez (2000);Flajolet, Gourdon, and Dumas (1995);Galambos and Simonelli (2004).
References
Adams, and Hedberg. 1999. Function Spaces and Potential Theory.
Bertrand, Bertrand, and Ovarlez. 2000.
“The Mellin Transform.” In
The Transforms and Applications Handbook. The Electrical Engineering Handbook Series.
Brychkov, Marichev, and Savischenko. 2019.
Handbook of Mellin Tranforms. Advances in Applied Mathematics.
Cohen. 1993.
“The Scale Representation.” IEEE Transactions on Signal Processing.
Davies. 2002. Integral Transforms and Their Applications.
De Sena, and Rocchesso. 2007.
“A Fast Mellin and Scale Transform.” EURASIP J. Appl. Signal Process.
Debnath, and Bhatta. 2014. Integral Transforms and Their Applications.
Flajolet, Gourdon, and Dumas. 1995.
“Mellin Transforms and Asymptotics: Harmonic Sums.” Theoretical Computer Science.
Hackmann, and Kuznetsov. 2016.
“Approximating Lévy Processes with Completely Monotone Jumps.” The Annals of Applied Probability.
Jánossy, and Messel. 1950.
“Fluctuations of the Electron-Photon Cascade - Moments of the Distribution.” Proceedings of the Physical Society. Section A.
Polyanin, and Manzhirov. 1998. Handbook of Integral Equations.
Schiff. 1999. The Laplace Transform: Theory and Applications.
Sena, and Rocchesso. 2004. “A Fast Mellin Transform with Applications in DAFX.”
Simon. 2015. Real Analysis. A Comprehensive Course in Analysis 1.0.